On the central nervous system of Smeagolidae and Rhodopidae, two families questionably allied with the Gymnomorpha (Gastropoda: Euthyneura)

The central nervous systems ( CNS ) of Smeagol manneringi Climo, 1980 (Smeagolidae), of Rhodope veranü Kölliker, 1847, and of Rhodope transtrosa Salvini-Plawén, 1989 are redescribed in detail. The smeagolid CNS exhibits diagnostic pulmonate characters (procerebrum, cerebral gland, dorsal bodies). Sharing a distinctly structured abdominal ganglion and other peculiarities, the Smeagolidae are closely related to the Onchidüdae, and both families are united as Onchidioidea. The consequences of this close relationship for the origin and evolution of the Gymnomorpha are discussed and the value of the pulmonate CNS for phylogenetics is reconsidered. On the basis of neural characters, which are correlated with the mode of breathing organs, the Pulmonata are divided into Basommatophora, Systellommatophora (Otinidae and Gymnomorpha) and Eupulmonata ( ord. nov .: Trimusculidae, Ellobüdae, Stylommatophora).
In contrast, the CNSs of the rhodopid species lack the pulmonate attributes, but show diagnostic opisthobranch characters such as a rhinophoral nerve. Accordingly, the Rhodopidae are excluded from the Pulmonata and are classified as a separate order Rhodopemorpha among the Opisthobranchia.     

中国红树林区的耳螺

耳嫘是一类特殊的原始有肺类软体动物,主要分布于热带、亚热带海陆交汇区的高潮带和潮上带.耳螺在红树林区广泛分布,且资源非常丰富,全世界已知的约240种耳螺中,至少有一半以上的种类在红树林区被记录.本文总结了耳螺与红树林的关系以及中国嗜盐耳螺的种类,综述了红树林区耳螺的种类组成、分布、生态功能、行为等的研究进展,报道了中国...     

Species diversity of Onchidiidae (Eupulmonata: Heterobranchia) on the mainland of China based on molecular data

The identification of members of the Onchidiidae is based on morphological characters; this is often time-consuming and can be inconclusive. In order to explore the species diversity of onchidiids in China, we provide a phylogeny constructed using partial sequences of two mitochondrial genes (16S rRNA and COI) and one nuclear ribosomal RNA gene (28S rRNA) from 32 samples comprising five genera. The topology, using both Bayesian and Maximum Likelihood inference methods, showed that the taxa clustered in two main groups of six species, one of which included Platevindex mortoni, Platevindex sp. and Onchidium ‘struma’; the other included Paraoncidium reevesii, Onchidella sp. and Peronia verruculata. It is clear that COI will be useful in discriminating onchidiid species-group taxa.     

Smeagolida,a new order of gymnomorph mollusc from New Zealand based on a new genus and species

Abstract

Smeagol manneringi n.gen. & sp. is erected as the only known representative of a new order, Smeagolida, and is compared with existing gymnomorph orders. The relative ranking of Gymnomorpha, Opisthobranchia, and Pulmonata is discussed, and use of the name Systellommatophora is abandoned. The gymnomorph slugs are interpreted as a polyphyletic assemblage of stem euthyneurans, but subclass Gymnomorpha is retained as a convenient grouping.     

Turtles as diapsid reptiles

Recent molecular studies of amniote relationships show turtles to be diapsid reptiles, related to the archosauromorph branch of saurian phylogeny. This conflicts with palaeontological data which shows turtles to be related either to anapsids, or to the lepidosauromorph branch within diapsids. Archosauromorph relationships of turtles have previously been proposed on the basis of neontological (mostly soft anatomy) characters. This paper reviews the neontological character evidence for turtle relationships and shows that most, but not all, of these characters are invalid in the reconstruction of turtle relationships within Amniota.     

The affinities of mites and ticks: a review

Mites and ticks can be divided into two well-defined clades, Anactinotrichida and Actinotrichida, for which a recent work formalized a suite of putative autapomorphies and reciprocal differences. Whether they are sister-taxa – forming a monophyletic Acari – is more controversial. Earlier supporters of two independent origins for mites largely failed to demonstrate convincing synapomorphies between either of the two lineages and other arachnid orders; although recent work on reproductive biology revealed explicit characters of this nature. Furthermore, some of the characters proposed in support of a monophyletic Acari do not stand up to detailed scrutiny when compared with Arachnida in general. Effective morphological comparisons between mites and other arachnids are hindered by incompatible nomenclature and long-standing, mite-specific characters which are difficult to score for other arachnids. Furthermore, taxon-specific characters restricted to individual mite groups have sometimes been treated erroneously as 'typical' for all Acari. Here, previous hypotheses of mite affinities are reviewed. Historically, authors have debated whether mites are basal arachnids or highly derived. Excluding weakly supported early hypotheses, mites have been resolved – in whole or in part – as sister-group of all other Arachnida (based on tagmosis), closely related to Opiliones (based mostly on genital morphology), Palpigradi (based on controversial interpretations of limb morphology), Solifugae (based mostly on the mouthparts, but now perhaps also reproductive characters) and Ricinulei (based on hexapodal larvae and perhaps mouthparts). We cannot provide a final resolution here, but we aim to highlight important character sets which should be included in subsequent phylogenetic analyses, as well as useful areas for future investigations: particularly tagmosis and the nature of the gnathosoma.     

Tertiary plotopterids (Aves, Plotopteridae) and a novel hypothesis on the phylogenetic relationships of penguins (Spheniscidae)

Plotopterids (Aves: Plotopteridae) are extinct wing-propelled diving birds which exhibit a strikingly similar wing morphology to penguins (Spheniscidae), but also share derived characters with 'pelecaniform' birds that are absent in penguins. The similarities between Plotopteridae and Spheniscidae have hitherto been attributed to convergence, and plotopterids were considered to be most closely related to the 'pelecaniform' Phalacrocoracidae (cormorants) and Anhingidae (anhingas). However, here I show that assignment of plotopterids to 'pelecaniform' birds does not necessarily preclude them from being the sister taxon of penguins. Cladistic analysis of 68 morphological characters resulted in sister group relationship between Plotopteridae and Spheniscidae, and the clade (Plotopteridae + Spheniscidae) was shown to be the sister taxon of the Suloidea, i.e. a clade including Sulidae (boobies and gannets), Phalacrocoracidae, and Anhingidae. Derived characters are discussed which support this novel hypothesis. Paedomorphosis probably accounts for the absence of derived characters in penguins that are shared by Plotopteridae and members of the Steganopodes. Plotopterids exemplify the importance of fossil birds for analyzing the phylogenetic relationships of modern taxa that exhibit a highly apomorphic morphology.     

Artifacts of Coding Amino Acids and Other Composite Characters for Phylogenetic Analysis

A phylogenetic analysis can be no better than the characters on which it is based. Just as it is inappropriate to code character states of individual characters as separate presence/absence characters, it is inappropriate to combine independent characters because not all information in the data is being utilized. Composite characters link otherwise discernible states from different characters together to form new character states. There are two related problems with this coding. First, there is a loss of hierarchic information between the reductive and composite characters when unordered states are used. Second, the linking of separate characters that occurs during the construction of composite character states can create putative synapomorphies that were not present in the separate characters. For amino acid characters, the problem may occur whenever more than one position of a codon is variable among the terminals sampled. Groups that are resolved as paraphyletic with reductive coding may be resolved as monophyletic with composite coding. The artificial character states indicated by the amino acid characters are unlikely to be congruent with the true gene tree.     

Deciduous Dentitions of Eocene Cebochoerid Artiodactyls and Cetartiodactyl Relationships

Deciduous lower premolars (milk teeth) of the Eocene artiodactyl family Cebochoeridae possess accessory denticles and are remarkably similar to both deciduous and adult teeth of the cetacean family Basilosauridae, suggesting that morphological characters of juvenile dentitions are important to understanding the phylogenetic origin of whales and morphological transitions in the cetartiodactyl lineage. Incorporation of these new characters into a larger phylogenetic analysis of morphological characters of artiodactyls, mesonychids, and basal and recent whales supports a monophyletic Cetartiodactyla, but does not directly support a whale–hippo relationship. However, the presence of accessory denticles on some artiodactyl dentitions weakens the morphological support for a monophyletic Artiodactyla, suggesting either that whales and cebochoerids may be more closely related than had been thought, or that cebochoerids share a developmental pathway with cetaceans.     

The middle ear of the skull of birds: the Pelecaniformes and Ciconiiformes

The anatomy of the middle ear region of the skull is described for the families of the Avian orders Pelecaniformes and Ciconiiformes. Emphasis is placed on the foramina and paths of the nerves and blood vessels. The morphology of the basicranium and quadrate is also discussed. Comparative analyses of the characters are used to assess taxonomic conclusions.
Extant Pelecaniformes consist of six families, four of which are monogenic: Phaethontidae, Pelecanidae, Anhingidae and Fregatidae; one is composed of two genera: Sulidae; and the last has three genera: Phalacrocoracidae. Several years ago a relationship was suggested which would ally the Phaethontidae and the Fregatidae. While these families share several non middle ear characters the anatomy of the middle ear is not compatible with any particular relationship. Indeed, several obvious differences are described. The data presented here are consistent with the idea that the Phaethontidae and the Fregatidae each form a separate group of Pelecaniform birds, with the rest of the families forming a third group. Several differences in the middle ear region of the species of Anhingidae suggest that the family may be composed of two genera.
While sharing many Ciconiiform characters the Ciconiidae have been shown not to be as closely related to the Ardeidae as they are to other families of Ciconiiformes. In addition, evidence is presented to support the recent idea that the three species of ibis (I. ibis, I. cinereus and I. leucocephalus ) be united within the genus Mycteria. Also supported is the notion that Balaeniceps is Pelecaniform in character, and not Ciconiiform.     

Anatomy and ultrastructure of the excretory system of a heart-bearing and a heart-less sacoglossan gastropod (Opisthobranchia, Sacoglossa)

The microanatomy and ultrastructure of the excretory system of the Sacoglossa have been investigated from two species by means of semithin serial sections, reconstructions and transmission electron microscopy. Whereas Bosellia mimetica shows a functional metanephridial system consisting of a heart with ventricle and auricle in a pericardium and a single kidney, Alderia modesta lacks heart and pericardium, possessing only several haemocoelic sinuses and a very long kidney. In B. mimetica podocytes as the site of ultrafiltration could be detected in the pericardial epithelium lining the auricular wall. The flat epithelium of the kidney with extensive basal infoldings and a dense microvillous border towards the luminal surface serves to modify the ultrafiltrate. In A. modesta podocytes are absent. Solitary rhogocytes (pore cells), the fine structure of which strongly resembles podocytes (meandering slits with diaphragms covered by extracellular matrix), occur in B. mimetica and A. modesta, representing additional loci of ultrafiltration. The presence of podocytes situated in the epicardial wall of the auricle is regarded as plesiomorphic for the Mollusca and confirmed for the Sacoglossa in this study, contradicting earlier assumptions of the loss of the primary site of ultrafiltration in the ancestors of the Opisthobranchia. In contrast to the likewise heart-less Rhodopidae with a pseudoprotonephridial ultrafiltration system, A. modesta shows no further modifications of the excretory system. Accepted: 7 May 2001     

The chemotaxonomic significance of the phenyl pyrone aloenin in the genus Aloe

The phenyl pyrone, aloenin was positively identified in 16 species in a greater chemotaxonomic study on 380 species of Aloe. A large number of species have previously been suggested to be related on the basis of their macromorphological characters. The leaf exudate composition of the 16 species are presented together with a summary of the salient morphological characters. The possible taxonomic relationships between aloenin producing species, not previously thought to be associated with one another are discussed and illustrates the need to explore additional characters of taxonomic value in this large genus of ca. 420 species where no natural classification system exists.     

Quantification of sexual dimorphism in Asellus aquaticus (Crustacea: Isopoda) using outline approaches

A marked sexual dimorphism is often observed in arthropods species in which males perform precopulatory mate guarding. It is generally thought to reflect the influence of sexual selection. Until now, sexual dimorphisms associated with mate guarding have mainly been qualitatively described. However, assessing the effects of sexual selection on sexual dimorphims requires a preliminary quantitative assessment of differences in morphology between sexes. Using Fourier analyses, we tested if morphological dimorphisms could be quantitatively assessed in the isopod Asellus aquaticus . In addition, we checked whether sexual dimorphism in shape was exclusively related to mate guarding through considering characters that are not, a priori , implicated in mating behaviour. To assess the potential role of sexual selection in shaping morphology, we then examined how dimorphic characters could influence males' pairing success. Three characters (pleotelson, paraeopods 4 and 5) differed significantly in shape between males and females. In addition, two characters (pleotelson and paraeopods 4) differed in shape between guarding males and non-guarding males, with the latter being closer in shape to females. This suggests that sexual selection may be partly responsible for the observed morphological divergence between sexes in A. aquaticus .  © 2002 The Linnean Society of London, Biological Society of the Linnean Society , 2002, 77 , 523–533.     

Sequencing of whole plastid genomes and nuclear ribosomal DNA of Diospyros species (Ebenaceae) endemic to New Caledonia: many species,little divergence

Background and Aims Some plant groups, especially on islands, have been shaped by strong ancestral bottlenecks and rapid, recent radiation of phenotypic characters. Single molecular markers are often not informative enough for phylogenetic reconstruction in such plant groups. Whole plastid genomes and nuclear ribosomal DNA (nrDNA) are viewed by many researchers as sources of information for phylogenetic reconstruction of groups in which expected levels of divergence in standard markers are low. Here we evaluate the usefulness of these data types to resolve phylogenetic relationships among closely related Diospyros species.Methods Twenty-two closely related Diospyros species from New Caledonia were investigated using whole plastid genomes and nrDNA data from low-coverage next-generation sequencing (NGS). Phylogenetic trees were inferred using maximum parsimony, maximum likelihood and Bayesian inference on separate plastid and nrDNA and combined matrices.Key Results The plastid and nrDNA sequences were, singly and together, unable to provide well supported phylogenetic relationships among the closely related New Caledonian Diospyros species. In the nrDNA, a 6-fold greater percentage of parsimony-informative characters compared with plastid DNA was found, but the total number of informative sites was greater for the much larger plastid DNA genomes. Combining the plastid and nuclear data improved resolution. Plastid results showed a trend towards geographical clustering of accessions rather than following taxonomic species.Conclusions In plant groups in which multiple plastid markers are not sufficiently informative, an investigation at the level of the entire plastid genome may also not be sufficient for detailed phylogenetic reconstruction. Sequencing of complete plastid genomes and nrDNA repeats seems to clarify some relationships among the New Caledonian Diospyros species, but the higher percentage of parsimony-informative characters in nrDNA compared with plastid DNA did not help to resolve the phylogenetic tree because the total number of variable sites was much lower than in the entire plastid genome. The geographical clustering of the individuals against a background of overall low sequence divergence could indicate transfer of plastid genomes due to hybridization and introgression following secondary contact.     

Relationships of the New Guinean songbird genera Amalocichla and Pachycare based on mitochondrial and nuclear DNA sequences

The New Guinean songbird fauna contains numerous enigmatic species and genera whose phylogenetic affinities have been difficult to resolve. Two such genera are ditypic Amalocichla and monotypic Pachycare. Here we obtained DNA sequences of two nuclear gene regions and a mitochondrial gene to ascertain the phylogenetic positions of these genera. Amalocichla was identified as the sister of the Australasian robins (Petroicidae) contrary to most recent classifications, which align it with the New Guinean mouse‐warblers Crateroscelis in the family Acanthizidae. The morphological characters used to place Amalocichla in the Acanthizidae appear to be convergent and linked to ground‐living adaptations. Pachycare was found to be most closely related to the Acanthizidae and not to the Pachycephalidae, corvine assemblage, or Petroicidae, as most commonly assumed. Morphological and behavioural characters support the molecular data in this conclusion. Previous taxonomic placements appear to have been based on superficial similarities in plumage coloration and vocal characterizations.     

Sex ratio control in pink salmon (<Emphasis Type="Italic">Oncorhynchus gorbuscha</Emphasis> and chum salmon (<Emphasis Type="Italic">O. keta</Emphasis>) populations: The possible causes and mechanisms of changes in the sex ratio

Long-term changes in the sex ratio have been studied in pink salmon (Oncorhynchus gorbuscha and chum salmon (O. keta) populations of Kamchatka and Sakhalin. It has been demonstrated that these changes are an adaptation to population dynamics: an increase in the population size is accompanied by a shift towards a higher proportion of males; a decrease in population size, by a shift towards a higher proportion of females. The correspondence between morphological and molecular characters in populations of the two species has been analyzed in order to determine the mechanism of sex ratio control. In some pink salmon and chum salmon populations, there is a discrepancy between sex identifications based on morphological characters and molecular markers. This discrepancy is assumed to be accounted for by sex inversion mechanisms, which may be population-or region-specific. In two cases, it has been found that the sex ratio discrepancy in populations is related to the numbers of fish in subsequent generations. These findings suggest that sex inversion may be related to population size control.     

Phylogeny of Callibaetis (Ephemeroptera: Baetidae) based on morphology of nymphs and adults

Callibaetis is considered to be one of the most problematic genera among mayflies by a series of taxonomic inaccuracies that have accumulated over the last two centuries. Despite these taxonomic problems, two independent hypotheses of species groups have been proposed. In the first hypothesis, three species groups for North America were proposed, and in the second, three species groups were proposed for South American. In these hypotheses, the generic delimitation and monophyly of Callibaetis have not been evaluated under a cladistic framework. Taking this into account, the objectives of this study were to verify the monophyly of Callibaetis and whether the groups of species proposed for the genus are corroborated as natural. The matrix included 128 morphological characters and one habitat character, 119 discrete characters were compiled (101 of nymphs and 18 of adults), and six imaginal characters are related to pigmentation pattern. Continuous characters were ratios and were represented by 10 characters (nine for nymphs and one for adults). The data set was analysed under implied weights. Group support was estimated with relative Bremer support and frequency differences. The results corroborated the monophyletic nature of Callibaetis and the generic status of Callibaetoides; however, the groups proposed for North and South American Callibaetis species were not corroborated. Our study indicated four groups of species for the genus, which we proposed as subgenera: Callibaetis, Abaetetuba subgen. n. Aiso subgen. n. and Cunhaporanga subgen. n.     

Exploring morphological evolution in relation to habitat moisture in the moss genus Fissidens using molecular data generated from herbarium specimens

Morphological evolution in mosses has long been hypothesized to accompany shifts in microhabitats, which can be tested using comparative phylogenetics. These lines of inquiry have been developed to include target capture sequencing, which can yield phylogenomic scale data from herbarium specimens. Here, we test the relationship between taxonomically important morphological characters in the moss genus Fissidens, using a 400-locus data set generated using a target-capture approach in tandem with a three-locus phylogeny generated using Sanger sequencing. Phylogenetic trees generated using ASTRAL and Bayesian inference were used to test the monophyly of subgenera/sections. These trees provide the basis for ancestral character state reconstructions and phylogenetic correlation analyses for five morphological characters and characters related to the moisture habitat, scored from the literature and by specimen inspection. Many of these characters exhibit statistically significant phylogenetic signal. Significant correlations were found between the limbidium (phyllid/leaf border of the gametophyte) and habitat moisture niche breadth, which could be interpreted as the more extensive limbidium enabling species to survive across a wider variety of habitats. We also found correlations between costa anatomy, peristome morphology, and the limbidium, which could reflect the evolutionary recruitment of genetic networks from the gametophyte to the sporophyte phase. The correlation found between average habitat moisture and the sexual system indicates that dioicous and polyoicous species are more likely to be found in moist habitats and that these higher moisture levels could be particularly, reproductively advantageous to species with separate sexes.     

Masticatory biomechanics and its relevance to early hominid phylogeny: an examination of palatal thickness using finite-element analysis

It has been proposed that morphological characters functionally related to mastication may be unreliable indicators of early hominid phylogeny. One hypothesis states that masticatory characters are highly prone to homoplasy. A second hypothesis states that such characters are likely to be morphologically integrated and thus violate the assumption of character independence implicit in all phylogenetic analyses. Evaluation of these hypotheses requires that masticatory features be accurately identified, but, to date, there have been relatively few attempts to test precisely which early hominid features are functionally related to chewing. This paper uses finite-element analysis to evaluate the functional relationships of a character--palatal thickness--that is one of several Paranthropus synapomorphies putatively related to mastication. A finite-element model of 145,680 elements was created from sixty-one 2-mm-thick CT scans of a Macaca fascicularis skull. The model was assigned the elastic properties of facial bone and loaded with muscle forces corresponding to the moment of centric occlusion during mastication. The model was constrained so as to produce a reaction force (corresponding to the bite force) at M(1). With a few exceptions, the strain patterns in the finite-element model compare well with those gathered from published and unpublished bone-strain experiments. The model was then modified to have a thick palate. The model was reloaded using an identical loading regime, and the strain patterns of the original and thick-palate models were compared. Although a thickened palate acts to reduce palatal strain, strains are elevated in other facial regions. This suggests that a thick palate would not have evolved in isolation as an adaptation to withstand masticatory stress. Rather, a thick palate may have evolved in concert with a suite of other facial features that share a stress-resistance function. This appears to be consistent with hypotheses positing that at least some facial features related to chewing evolved in an integrated fashion. More functional studies of other facial features are needed, as are formal studies of morphological integration.     

异鲴的骨骼形态及其属的分类位置

对异鲴的骨骼形态进行了详细的描述并与丹亚科及鲴亚科代表种的骨骼特征进行了比较。结果显示异鲴与丹亚科在骨骼学性状缺乏共同离征,一系列的离征却表明它与再生鲴亚科鱼类紧密相关。这些离征包括：咽骨形态独特,前臂略长或与后臂等长;下咽齿侧扁,有明显的咀嚼面;基枕骨具有向下弯曲的基枕骨突,咽突而发达,椭圆形且向前突出;穿行于基枕骨的背大动脉通道接近咽突长;副蝶骨具有发达的龙骨突;前上颌骨短宽,下边缘为软骨;上颌骨外侧具突起;齿骨前背缘有外侧等。异鲴之置于丹亚科仅依据他们在围眶骨系的形态及排列上的相似性,而它和鲴亚科鱼类具有的一些共同离征表明它们可以形成姐妹群。因此,异鲴属在鲤科中的分类位置应该更加接近鲴亚科。